[Haskell-cafe] List spine traversal

[Don Stewart]

andrewhhunter:
> On Mon, Jun 29, 2009 at 11:30 PM, Ryan Ingram<ryani.spam at gmail.com> wrote:
> > There can't be a way to do so that is pure, because such a function
> > could distinguish between
> >> xs1 = () : xs1
> > and
> >> xs2 = f () where f () = () : f ()
> >
> 
> But doesn't seq and friends cause many of our normal referential
> transparency guarantees to be invalid?

Equational reasoning, in the presence of bottoms, anyway.

-- Don